Controllable Preparation Of Vanadium Oxide And Its Zinc Storage Mechanism

The aqueous rechargeable zinc ion batteries（ZIBs）are recognized as a promising alternative energy device for large-scale energy storage systems.The development of high performance cathode materials is one of the significant factors for the commercial application of ZIBs.Vanadium-based materials have attracted much attention as the ZIBs cathode due to their rich valence states,diverse structures and high capacity.However,its inherent low conductivity,unstable interlayer structure and slow Zn²⁺diffusion kinetics are the main challenges for the vanadium oxide.In order to explore the vanadium-based cathodes with high electrochemical property for zinc ion storage,two kinds of vanadium oxides were designed through structural design and optimization of the materials.The electrochemical property and zinc storage mechanism were further revealed,which were summarized as follows:（1）Intercalating conductive polymer poly（3,4-ethylenedioxythiophene）（PEDOT）into vanadium oxide（named as PEDOT-VO）by a simple and rapid hydrothermal method is designed to enhance the structure stability,Zn²⁺intercalation/deintercalation,and electron transfer kinetics of V₂O₅.The larger interlayer spacing of 13.95（?）（compared to 4.38（?）for bare V₂O₅）is constructed by conductive polymer intercalation.As ZIB cathode materials,the as-prepared PEDOT-VO cathodes deliver a high specific capacity of 370.5 m Ah g^-1at 0.5 A g^-1 and 175 m Ah g^-1 even at 50 A g^-1.Moreover,the long-life cycling of over 1000 cycles with a specific capacity of 310.1 m Ah g^-1 is also achieved.Quantification calculation results reveal that pseudo-capacitance mainly contributes to zinc-ion storage,leading to ultrahigh rate capability.Finally,the Zn²⁺storage mechanism of PEDOT-VO electrode was elucidated by ex-situ XRD and XPS analysis.（2）The V₁₀O₂₄·n H₂O with large interlayer spacing and stable structure was successfully synthesized inducing VO₂ phase transition through a simple refluxing process.When was applied as a high-performance cathode material for ZIBs,It delivers that a high reversible capacity,ultra-high rate performance,and long-term cycling life.The superior electrochemical property attribute to the synergistic effects of the ultra-thin nanoribbons structures,oxygen vacancy and water molecules.On the one hand,the ultrathin nanoribbon structure and oxygen vacancy are beneficial to the electron/ion transport kinetics of V₁₀O₂₄·n H₂O electrode in the cycle process for ZIBs system.On the other hand,interlayer water molecules can effectively maintain the structural stability of V₁₀O₂₄·n H₂O.Furthermore,ex-situ XRD and XPS analysis elucidated the Zn²⁺storage mechanism of the V₁₀O₂₄·n H₂O cathode.